1. Field Of The Invention
This invention relates to structures, particularly to structural columns that are integral and load-bearing parts of structures.
2. Prior Art
Certain grains, feed ingredients, seed, and various other organic or inorganic materials in either granular, powdered, liquid, or other particulate form are stored in multiple bins, such as an array of square or polygonal bins. Examples of such bins are shown in U.S. Pat. No. 521,951, to Fallis, 1894; U.S. Pat. No. 3,327,870, to Fairchild, 1967; U.S. Pat. No. 4,218,859, to Sams, 1980; and U.S. Pat. No. 4,893,445, to Hefer et al., 1990. The bins are usually assembled in one of two ways: (1) on their sides, as in the Sams patent, and then lifted on top of a substantial support structure such as an I-beam support structure or some other support structure, using a crane; or (2) the structures are assembled from the bottom up, atop a separate, substantial support structure, where each piece is individually lifted into place, requiring larger cranes as the vertical height increases. The Fallis patent discloses a storage bin that is hexagonal in horizontal cross section, and that has corner plates that join the walls of the bin. However, these corner plates are not load-bearing and do not form structural columns that can extend below the bin to support the entire structure. Consequently, if the bin must be elevated to accommodate a hopper, for example, the structure must be lifted onto a separate support structure. Furthermore, if the structure is tall, workers are exposed to dangerous heights during construction.
In cases where the columns are continuous or integral and consist of modular pieces, as disclosed in the Fairchild patent and U.S. Pat. No. 4,008,553 to Oliver (1977), the bins must still be constructed using cranes if the height of such bins exceeds a certain vertical limit. In addition, as illustrated in FIGS. 1 and 2 (Prior Art), a substantial structural support such as an I-beam frame 310a or 310b or concrete pillars is usually required, especially if the bins have hoppers. Furthermore, these types of support structures can limit the vertical placement of the hoppers such that top edges 309 of all hoppers usually must be at the same vertical height. Other configurations which allow the tops of hoppers to begin at different vertical heights from each other are very cumbersome and difficult to build using current methods, and so such configurations are seldom used, even though advantages often exist in having tops of hoppers at different vertical heights.
Where columns of bin structures consist of elements that are all one length, such as in U.S. Pat. No. 3,706,169 to Eberhard (1972) and the Sams patent, the vertical height of a structure is limited. If one column can be connected to the top of another column, a dangerous environment where workers are suspended high above the ground to connect pieces is created, and a crane is often required. This is usually the case with current methods of constructing such multi-compartmented storage structures. Crane use is further required when constructing process towers, such as 308a and 308b in FIGS. 1 and 2 (Prior Art), where distribution and/or processing equipment is located.
The cost of I-beam or concrete support structures and crane use, associated with the construction of multiple square or polygonal bins as described above, may not be limiting for commodities that currently have relatively high value, such as seed and certain feed ingredients, but these costs are very often limiting for low-value commodities, such as cereal grains, corn, or soybeans. The use of multiple polygonal storage bins is often described as segregated storage, because the contents of the bins are segregated based on different characteristics. Segregation can be based on such characteristics as, including but not limited to, the following: (a) ingredient origin, (b) plant variety, (c) protein level, (d) moisture level, (e) quality, (f) particle size, (g) field origin, (h) proximity of growing location to potential contaminant pollen sources, (i) growing conditions, (j) farming practices, for example, organic versus non-organic, (k) foreign matter level, or (l) GMO status.
Despite advantages of segregated storage, which will be described below, those industries related to bulk commodity production have been slow to adopt segregated storage, even with tremendous customer, societal, and governmental pressures to do so. The reluctance to incorporate a segregated-storage approach to bulk commodities is partially due to the relatively high cost of current designs and methods of constructing segregated storage.
The conventional approach for storage of grains, commodities, and ingredients has been to use bulk storage, that is, very large, round grain bins that accommodate contents that are usually of different varieties, from different growers, with different harvest locations or dates, or with different characteristics, for example. Such bulk storage can reduce costs associated with handling, and the large, round grain bins are also relatively inexpensive to purchase and to build, compared to segregated storage options that are currently available. But bulk storage has its disadvantages, such as the inability to trace contents to a precise time and location of manufacture or production, and difficulty in keeping products with different characteristics separate. Other changes in storage needs have occurred over the last decade, such as the introduction of identity preservation and genetic engineering techniques that have produced so-called genetically modified organisms (GMOs). As a result, the storage industry has recognized a need to shift towards segregated storage, where contents can be traced to their origin, and away from bulk storage, which has certain liabilities that may not have existed in the past. This increased need for segregation stems from governmental, societal, and consumer pressures.
The seed industry can be a model for the grain industry, and to some extent, the feed industry. Historically, the seed industry has segregated seeds not only by variety, but also by grower, year, and location of production. In contrast, the grain industry has conventionally stored grain from many points of origin within a single, large bulk grain bin, often co-mingling grains of substantially different quality, with different characteristics, or even of different varieties. Stricter purity requirements are another factor that is forcing the grain industry to re-think its bulk storage practices, especially as governments accept increasingly lower levels of GMO in non-GMO items, and as customers, such as millers, brewers, and other processors, demand better identity preservation to acquire the product with the characteristics that best serves their purposes.
Not only has segregation pressure increased within the grain industry, it has also risen in the animal feed manufacturing industry, especially due to risks associated with food safety. In particular, a great concern has recently arisen with Bovine Spongiform Encephalopathy, also known as Mad Cow Disease. Animals that consume feed that is contaminated with infectious animal by-products can contract the disease. The disease can be transmitted to humans who eat infectious portions of a diseased animal. The disease has now been documented to be in the United States. Complying with government regulations, such as those proposed recently by the European Union that require the ability of all feed ingredients to be traced to their point of origin, is difficult when utilizing large bulk storage. As a result, the feed manufacturing industry also has a need for more multi-compartmentalized bins, not only for the micro-ingredients (that is, feed ingredients that are used in very small proportions, such as vitamins, minerals, and growth enhancers) that have conventionally been stored in multi-compartmentalized bins, but now also for main ingredient storage, which has been handled in a similar manner as other bulk commodity storage. The transformation of the grain industry, and to some extent the feed industry, from a bulk storage mentality to a more refined, segregated storage system is limited in large part by the relatively large cost of segregated storage as it currently exists compared to the cost of bulk storage.
Typically, for multi-bin arrays, support structures, like 310a and 310b, shown in FIGS. 1 and 2 (Prior Art), are built first. These structures generally are a framework of I-beams, concrete pillars, or some other hefty assemblage. Then, individual storage bins are built either on top of the support structure, or in a workshop, or on the ground at the jobsite, and then lifted into place with a crane. Building the storage unit on top of the support structure requires that every piece be lifted up into place, requiring construction workers to continually build or move scaffolding up to increasingly deadly heights as the building progresses. In most cases, cranes are generally used to lift parts or entire bins into place, using skilled ironworkers that are competent to safely perform the work. Use of skilled labor also increases the cost of the construction project compared to jacking and assembling a structure at or near ground level using relatively unskilled labor.
Another limitation to some types of existing polygonal storage structures is transportation costs and size limits associated with bins that are completely assembled or prefabricated in workshops elsewhere. Although lifting prefabricated storage bins onto a support structure requires fewer crane hours than lifting each part into place, lifting a complete silo requires a larger, more costly crane than lifting individual parts. Furthermore, pre-fabricated tanks that are lifted onto a support structure still require that the vertical sides be bolted or welded together by a skilled worker that must traverse the entire vertical length of adjoining walls to bolt, fasten, or weld them together.
The typical, conventional corrugated steel flat bottom silo may be an adequate choice if only a single bin is required. However, if multiple bins are needed, the round grain bin has limitations. For example, a larger footprint (more land area) is needed for multiple round grain bins, compared to the amount of land required for conventional square or hexagonal bin arrays that share common walls. A second limitation of conventional corrugated steel flat bottom round grain bins is that they cannot discharge all of the grain by gravity, unless they are positioned on a concrete hopper, or they include devices such as sweep augers or air sweeps, or manual labor is used. If manual labor is used, strict confined-space-bin-entry safety procedures must be followed. A third limitation of steel round grain bins is the size constraints such bins are subject to under current practices. Even though steel round grain bins can achieve huge diameters, generally up to about 32 meters, difficulties have been experienced in bins with larger diameters. These difficulties, in many cases, are partially due to inadequate stiffener design. A fourth limitation is in distribution spouting, a method of filling bins involving spouts that are typically angled at 45 degrees from vertical, and that are erected above the bins. To achieve the recommended 45-degree spouting angle, a very high head house, which supports the spouting, would need to be built.
Despite these limitations of the round grain bin, a great advantage of it is the use of a relatively safe and inexpensive method of jack-lifting construction, which has not yet been applied to a multi-bin array with shared walls. One such method, illustrated in FIG. 3 (Prior Art) and disclosed in U.S. Pat. No. 6,311,952 to Bainter (2001), involves hydraulic jacks, which are arranged along the perimeter of a roof assembly 301 of the bin. The roof assembly is usually assembled of one or two horizontal levels, or ‘rings’ 302, of wall panels, and then a roof is built on top of these first rings, while at or near ground level. Jacks 303 are anchored to a foundation stem wall 304 and bolted onto roof assembly 301. The jacks then lift roof assembly 301 so another ring of body sheets can be added below it. Once the next ring is added, the jacks are detached from assembly 301 and reattached to the next lower ring, which is then jack-lifted, and another ring of wall panels is attached. This process is repeated until the bin has reached a desired height. When all body sheet rings have been added, the bin is anchored to a foundation, such as concrete foundation stem wall 304, and jacks 303 are removed.
Such jacking methods, however, have not been used to build a structure comprising an array of polygonal bins, most likely because conventional designs of shared-wall bin arrays are not conducive to jack-lifting. Developing a design that allows jack-lifting would present a considerable savings in construction costs. The method of jack-lifting, as described, does not require an expensive crane to lift every part into place or to lift complete silos onto a structure. The labor does not need to be highly skilled, since the required tasks simply involve assembling sheet metal parts, using wrenches or power tools, working at or near ground level, and using jacks to raise the assembled structure. And a safer work environment is created, which further reduces job-related liabilities. These factors contribute to the low cost of erecting corrugated steel flat bottom round grain bins, and could conceivably be applied to building a structure comprising multiple compartments and multiple levels.
The conventional corrugated steel round grain bin with a hopper bottom can empty all stored particulate by gravity, unlike the flat round bottom grain bin discussed above. However, like its flat bottom cousin, its diameter is limited in size due to structural support considerations. Like the flat bottom round grain bin, the hopper bottom round grain bin uses land space inefficiently if more than one is needed. Furthermore, constructing a hopper bottom round grain bin generally costs significantly more than a flat bottom round grain bin. The increased cost is because a hopper 312 and a support structure 311, as illustrated in FIG. 2 (Prior Art), have to be built independently of the grain bin. Then, the entire grain bin, although having been completely constructed using an economical jack-lifting method, has to be lifted on top of the hopper and support structure with an expensive crane.
The advantage of an array of shared-wall bins (versus multiple round bins) is the efficient use of material and land area, but this advantage is at present overcome by the relatively expensive methods of constructing such an array. If the more cost-efficient method of jack-lifting can be used to construct a shared-wall multi-bin array, then in terms of cost, the advantages of constructing a multi-bin array reasonably approaches or outweighs those of constructing a plurality of round grain bins. Cost would no longer be the limiting factor of installing segregated storage.